Volatile Liquid Anesthetics: Fluorinated Compounds
These agents are liquids converted into vapor before delivery to the patient using specialized vaporizers within the anesthesia machine. Classic representatives include halothane, enflurane, and isoflurane, as well as the more modern sevoflurane and desflurane.
Isoflurane is an isomer of enflurane with an improved safety profile compared to its predecessors. It does not trigger cardiac arrhythmias and is entirely devoid of hepatotoxic and nephrotoxic properties, meaning it does not damage the liver or kidneys.
Sevoflurane is one of the most popular modern agents in this group. It possesses several outstanding pharmacokinetic characteristics:
- Very rapid induction of the surgical stage of anesthesia.
- Exceptionally easy control over the depth of anesthesia during surgery.
- Rapid emergence and recovery of the patient from anesthesia.
Furthermore, sevoflurane exerts minimal adverse effects on internal organs, with weak effects on hemodynamics (cardiovascular function) and respiration. Due to this safety profile, it is widely used not only in large inpatient facilities but also in outpatient surgery.
Volatile Liquid Anesthetics: Ethers
The classic representative of this group is diethyl ether (ether for anesthesia). Today, it is rarely used in modern practice due to significant drawbacks, despite its unquestionable pharmacodynamic benefits.
Advantages of ether:
- Very high anesthetic potency.
- A wide therapeutic index, providing a safe dosage range (difficult to overdose to a fatal outcome).
- Potent analgesia and excellent skeletal muscle relaxation.
Disadvantages and side effects:
- Extremely slow induction and a prolonged, pronounced excitement stage.
- Slow emergence (recovery takes about 30 minutes, and complete restoration of central nervous system function takes several hours).
- Local irritant effect. Ether vapors stimulate salivary and bronchial gland secretion. This can lead to reflex respiratory depression, a sharp decrease in heart rate (bradycardia), and vomiting.
It is also important to remember physical and chemical risks: ether vapors are extremely flammable and become explosive when mixed with air (or nitrous oxide).
Gaseous Anesthetic Agents
Nitrous oxide ($N_2O$), also known as dinitrogen monoxide, is a colorless, odorless gas. It is non-flammable on its own but actively supports combustion.
The main feature of nitrous oxide is its low anesthetic potency. Achieving a deep surgical stage of anesthesia using this gas alone is only possible under hyperbaric conditions (increased pressure). Under normal conditions, the effect strictly depends on the concentration of the substance in the inspired mixture:
- 20% $N_2O$ provides pronounced analgesia.
- 80% $N_2O$ produces only superficial anesthesia without muscle relaxation.
Rules of application: To prevent tissue hypoxia, nitrous oxide must never be administered in pure form. It is always used in a mixture with oxygen. The proportion of nitrous oxide must not exceed 80%, and the oxygen fraction must be at least 20% (roughly corresponding to the oxygen content in ambient air).
Anesthesia with this gas mixture is rapid, the excitement stage is absent, and the agent is easily controlled. Patient emergence occurs within the first few minutes after gas delivery is stopped.
Nitrous oxide is actively used for analgesia in short surgical procedures (e.g., in dentistry and gynecology), for pain relief during labor, and in emergency medicine for severe pain management in myocardial infarction and acute coronary syndrome.